Royal Irish Academy. 153 



From the agreement in the configuration of the under surface of 

 the hody of the vertebra? of the fossil with that in the vertebrae of 

 the BoEe and Pythons more nearly than with the Colubri, and in 

 none of the differences above noticed indicating any obstacle to the 

 entrapping and destroying a living struggling prey, as well as from 

 the length (11 feet) which it may be inferred the creature attained, 

 Mr. Owen concludes it was not provided with poisonous fangs. 

 Serpents of similar dimensions exist in the present day only in 

 tropical regions, and their food consists principally of the warm- 

 Dlooded animals. Mr. Owen therefore in conclusion states, that had 

 no evidence been obtained of birds or mammals in the London clay, 

 he would have felt persuaded that they must have coexisted with 

 the Palaophis Toliapicus. 



ROYAL IRISH ACADEMY. 



Feb. 24. — A communication was read, entitled, " Justification of 

 Mrs. Somerville's Experiments upon the magnetizing Power of the 

 more refrangible solar Rays*." By George James Knox, Esq. and 

 the Rev. Thomas Knox. 



Professor Morichini of Rome was the first to observe that steel, 

 when exposed to the violet rays of the solar spectrum, becomes 

 magnetic. Similar experiments were tried by Mr. Christie in 1824; 

 but the most accurate experiments upon this subject have been per- 

 formed by Mrs. Somerville in 1825, who determined that not only 

 violet, but indigo, blue and green, develope magnetism in the ex- 

 posed end of a needle, while yellow, orange, and red produce no 

 sensible effect. As many philosophers have failed in repeating these 

 experiments, we were induced, in the course of the summer, to un- 

 dertake the investigation of this subject, " which has so often dis- 

 turbed science." Having procured several hundred needles, of dif- 

 ferent lengths and thicknesses, and having ascertained that they 

 were perfectly free from magnetism, we enveloped them in white 

 paper, leaving one of their extreme ends uncovered. Taking ad- 

 vantage of a favourable day for trying experiments upon the che- 

 mical ray, (known by the few seconds required to blacken chloride 

 of silver,) we placed the needles at right angles to the magnetic 

 meridian, and exposed them for three hours, from eleven to one, to 

 the differently refrangible rays of the sun, under coloured glasses. 

 Those beneath the red, orange, and yellow, showed no trace of mag- 

 netism, while those beneath the blue, green, and violet, exhibited, 

 the two first feeble, but the last strong traces of magnetism. 



To determine how far the oxidating power of the violet ray is 

 concerned in the phenomena, we exposed to the different coloured 

 lights needles whose extremities had been previously dipped in nitric 

 acid, and found that they became magnetic (the exposed end having 

 been made a north pole) in a much shorter time than the others, 



* Phil. Trans, vol. cxvi. 1826. (Reprinted in Phil. Mag. First Series, 

 vol. lxviii. p. 168.) 



